<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <div id="app"></div>

    <script src="./src/react.js"></script>
    <script src="./src/react-dom.js"></script>
    <script src="./src/babel.js"></script>

    <script type="text/babel">
   
     class Biaodan extends React.Component{
        constructor(){
            super();
            this.user = React.createRef()
        }
        add=()=>{
            // console.log(this.user.current.value)
            console.log( document.getElementById("username").value )
        }
     
        render(){
       
            return (
            <div>   
                <input type="text" defaultValue="aaa" id="username" ref={this.user}/> 
                <input type="button" value="提交" onClick={this.add}/>
         
            </div>
            )
        }
     }




        ReactDOM.render(
            <div>
                <Biaodan></Biaodan>
            </div>,
            document.getElementById("app")
        )
        
    </script>

</body>
</html>